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Strengthening El Niño May Trigger Wet Winter In San Diego

Photo credit: U.S. Navy

Warming sea surface temperatures in the Equatorial Pacific Ocean, shown in red, signal a strengthening El Niño, July 2015.

The strongest El Niño in nearly 20 years seems to be developing in the tropical Pacific Ocean, according to the latest forecast by the National Oceanic Atmospheric Administration.

The strongest El Niño in nearly 20 years seems to be developing in the tropical Pacific Ocean, according to the latest forecast by the National Oceanic Atmospheric Administration.

The highly watched weather phenomenon has the potential to temporarily change the heating pattern of the atmosphere and pull the Pacific jet stream farther south.

Previous strong El Niños have played havoc on weather systems across the globe, causing heavy rain and mudslides in some areas, and drought in others. They've also disrupted the marine food chain.

In San Diego, a strong El Niño is correlated with above average rainfall of 20 percent or more — good news for a region gripped by four years of drought.

The last severe El Niño to hit the region was in 1997-1998, when 17 inches of rainfall soaked San Diego and strong surf caused extensive coastal erosion.

“That event, it was warmer in mid-July than it is at the moment,” said Dave Pierce, climate researcher with Scripps Institution of Oceanography in La Jolla.

Current sea surface temperatures in the Equatorial Pacific are 4 degrees above average, said Pierce. In July 1997, temperatures were 6 degrees higher than normal.

“So it’s not as big as the '97-'98 event, but it’s bigger than any we’ve had since then,” he said.

Pierce said the brewing El Niño could continue to strengthen, or it could diminish a bit.

“There’s this predictable component, which has to do with how the ocean and atmosphere interact between each other. But there’s also an unpredictable component depending on how particular typhoons and other storms in the tropical Pacific affect the El Niño,” Pierce said.

He emphasized that an El Niño doesn't always guarantee a wet year for Southern California.

"But the stronger the event is, the more likely you are to have that response," Pierce said.

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